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AQA GCSE 1a-2 Using Energy

AQA GCSE 1a-2 Using Energy. AQA GCSE Physics pages 38 to 49 AQA GCSE Science pages 242 to 253. April 10 th 2010. AQA GCSE Specification. ENERGY EFFICIENCY 11.2 What is meant by the efficient use of energy? Using skills, knowledge and understanding of how science works:

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AQA GCSE 1a-2 Using Energy

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  1. AQA GCSE 1a-2Using Energy AQA GCSE Physics pages 38 to 49 AQA GCSE Science pages 242 to 253 April 10th 2010

  2. AQA GCSE Specification ENERGY EFFICIENCY 11.2 What is meant by the efficient use of energy? Using skills, knowledge and understanding of how science works: • to describe the intended energy transfers/transformations and the main energy wastages that occur with a range of devices • to calculate the efficiency of a device using: efficiency = useful energy transferred by the device / total energy supplied to the device • to evaluate the effectiveness and cost effectiveness of methods used to reduce energy consumption. Skills, knowledge and understanding of how science works set in the context of: • Energy cannot be created or destroyed. It can only be transformed from one form to another form. • When energy is transferred and/or transformed only part of it may be usefully transferred/transformed. • Energy which is not transferred/transformed in a useful way is wasted. • Both wasted energy and the energy which is usefully transferred/transformed are eventually transferred to their surroundings which become warmer. • Energy becomes increasingly spread out and becomes increasingly more difficult to use for further energy transformations. • The greater the percentage of the energy that is usefully transformed in a device, the more efficient the device is.

  3. Energy Energy is required to do work. Fuels are burnt to release energy The Sun is the ultimate source of most of our energy on Earth.

  4. Forms of energy Energy can exist in many forms. CHEMICAL ENERGY This is energy that is released when chemical reactions take place. Sources of chemical energy include: fuel, food and batteries.

  5. Gravitational potential energy being converted into kinetic energy. KINETIC ENERGY This is the energy possessed by a moving object. Kinetic energy increases is the object’s speed is increased. GRAVITATIONAL POTENTIAL ENERGY This is the energy possessed an object due to its position. The gravitational potential energy of an object increases if it is raised upwards.

  6. ELASTIC ENERGY This is the energy stored in a stretched or squashed object - also known as strain energy ELECTRICAL ENERGY This is the energy transferred by an electric current. SOUND ENERGY This is energy in the form of a sound wave.

  7. THERMAL ENERGY This is the energy of an object due to its temperature. - also known as heat energy LIGHT ENERGY This is energy in the form of visible electromagnetic radiation. NUCLEAR ENERGY This is energy that is released when nuclear reactions take place. This is the source of the Sun’s energy.

  8. Useful and wasted energy Useful energy This is energy transferred to where it is wanted in the form it is wanted. Wasted energy This is energy transferred to where it is not wanted in the form it is not wanted.

  9. USEFUL OUTPUT ENERGY INPUT ENERGY DEVICE CAUSING ENERGY CHANGE WASTED ENERGY Energy flow diagrams GENERAL DIAGRAM

  10. lightbulb An electric light bulb electrical energy light energy heat energy

  11. microphone Microphone sound energy electrical energy heat energy

  12. car engine Car engine chemical energy kinetic energy heat & sound energy

  13. plants Photosynthesis light energy chemical energy heat energy

  14. Complete the table below: kinetic kinetic Falling object chemical kinetic

  15. Forms of energyNotes questions from pages 38/242 & 39/243 • Copy the list of different forms of energy on page 38/242. • Copy and answer questions (a), (b), (c) and (d) on pages 38/242 and 39/243. • Copy the Key Points on page 39/243. • Answer the summary questions on page 39/243.

  16. In text questions: Electrical energy. High speed train (Train de grand vitesse) It is lost to the surroundings through heat transfer. From gravitational potential energy. Summary questions: (a) Gravitational potential, kinetic (b) Electrical, thermal 2. (a) For example: a candle and a torch. A candle transfers chemical energy to light and heat. a torch transfers chemical to electrical and then light and heat. (b) (i) A torch is usually more convenient. (ii) This is a matter of opinion. 3. Mechanical energy is transformed to gravitational potential energy as the pile driver lifts the heavy steel block. As the steel block falls, the gravitational potential energy is transformed into kinetic energy of the block. When the block hits the ground the kinetic energy is transformed into heat and sound energy. Forms of energy ANSWERS

  17. Conservation of energy Energy cannot be created or destroyed. It can only be transformed from one form to another form. Conservation of energy also means that the total energy in the universe stays constant.

  18. MINIMUM MAXIMUM MAXIMUM ZERO Pendulum oscillation GRAVITATIOINAL POTENTIAL ENERGY KINETIC ENERGY The total energy, gravitational potential plus kinetic, remains the same if there are no significant resistive forces

  19. Conservation of energyNotes questions from pages 40/244 & 41/245 • What is meant by the conservation of energy? • Explain how energy is conserved in (a) the oscillation of a pendulum and (b) a bungee jump. • Copy and answer questions (a), (b) and (c) on pages 40/244 and 41/245. • Copy the Key Points on page 41/245. • Answer the summary questions on page 41/245.

  20. In text questions: (a) (i) Kinetic energy changes to thermal energy in the brakes and thermal energy of the surroundings. (ii) Kinetic energy changes to gravitational potential energy as it climbs the hill. The gravitational potential energy changes back to kinetic energy as it descends. Thermal energy of the surroundings due to air resistance and friction is produced throughout. (b) It is transformed by air resistance to thermal energy of the surroundings. (c) Start → GPE → KE + Heat energy → Strain energy + Heat energy → GPE→ KE + Heat energy → etc… Summary questions: 1. (a) Gravitational potential, electrical, thermal, gravitational potential. 2. (a) On descent: Gravitational potential energy → kinetic energy + thermal energy due to air resistance. On impact: Kinetic energy → elastic energy of trampoline + thermal energy due to impact + sound. On ascent:Elastic energy of trampoline → kinetic energy → gravitational potential energy + thermal energy due to air resistance. (b) The ball has less energy at the top of its bounce than at the point of release. (c) (i) Type of trampoline (ii) Categoric 3. Elastic energy of the rubber straps is transformed into kinetic energy of the capsule. The kinetic energy is transformed into gravitational potential energy as the capsule rises to the top of its flight, etc. as in bungee jumper. Conservation of energy ANSWERS

  21. Energy spreading out How energy becomes less useful Wasted energy spreads out into the surroundings. This is usually in the form of heat energy causing the energy changing device and its surroundings to become warmer. It is very difficult to ‘concentrate’ this energy again to make use of it. Friction in machines is a common cause of energy being wasted to heat.

  22. Useful energyNotes questions from pages 42/246 & 43/247 • Give two examples each of (a) useful energy and (b) wasted energy. • What effect, energy wise, does the force of friction have in machines? • Copy out the paragraph under the heading ‘Spreading out’ on page 43/247. • Copy and answer questions (a), (b) and (c) on pages 42/246 and 43/247. • Copy the Key Points on page 43/247. • Answer the summary questions on page 43/247.

  23. In text questions: It is gained by the surroundings as thermal energy. It is transferred to the surroundings as thermal energy by friction between its moving parts and in the brakes, and by air resistance. The hot water mixes with the cold water. Its thermal energy spreads out and can’t be used again. Summary questions: 1. (a) useful: thermal energy of the element; wasted: thermal energy of the case (b) useful: light and sound energy; wasted: thermal energy (c) useful: thermal energy of the water; wasted: thermal energy of the steam and of the kettle itself (d) useful: sound energy; wasted: thermal energy in the wire 2. (a) It would heat up . The lubricating oil and the gears would get hot. (b) The feet would get too hot and sweaty. (c) The drill would heat up and smoke if it burns the wood. 3. Air resistance causes friction as the pendulum swings. This produces heat and so the pendulum loses energy to the surroundings and stops. Useful energyANSWERS

  24. Energy measurement Energy is measured in joules (J) To lift an apple upwards by one metre requires about one joule of energy. 1 kilojoule (kJ) = 1 000 J 1 megajoule (MJ) = 1 000 000 J

  25. Other energy measurement examples

  26. Energy efficiency Energy efficiency is a measure of how usefully energy is used by a device. useful energy transferred by the device efficiency = total energy supplied to the device As the useful energy can never be greater than the energy supplied the maximum efficiency possible is 1.0

  27. Energy efficient light bulbs • These produce more useful light energy for the same amount of input electrical energy. • They waste less energy to heat.

  28. useful energy transferred by the device efficiency = total energy supplied to the device Question 1 Calculate the efficiency of an electric motor if it produces 48J of useful kinetic energy when supplied with 80J of electrical energy. efficiency = 48J ÷ 80J efficiency of the motor = 0.6

  29. useful energy transferred by the device efficiency = total energy supplied to the device Question 2 Calculate the useful light output of a light bulb of efficiency 0.20 when it is of an electric motor if it supplied with 400J of electrical energy. 0.20 = useful energy÷ 400J useful energy = 0.20 x 400J light output = 80J

  30. Percentage efficiency percentage efficiency = efficiency x 100 The greater the percentage of the energy that is usefully transformed in a device, the more efficient the device is. The maximum percentage efficiency is 100%

  31. useful energy transferred by the device efficiency = total energy supplied to the device Question Calculate the percentage efficiency of a light bulb if it produces 30J of light when supplied with 240J of electrical energy. efficiency = 30J ÷ 240J = 0.125 % efficiency = efficiency x 100 Percentage efficiency of light bulb = 12.5%

  32. Complete Answers 60 0.40 40% 200 0.80 80% 10 40 20% 24 56 0.30 120 0.50 50%

  33. USEFUL OUTPUT INPUT Device WASTED OUTPUT Sankey Diagrams These are energy flow diagrams that show how well a device uses energy. The width of the flow arrows is proportional to the amount of energy Wasted energy is shown flowing downwards.

  34. KINETIC ENERGY CHEMICAL ENERGY CAR HEAT & SOUND ENERGY Question Draw a Sankey diagram for car of efficiency 20% The kinetic energy arrow should be 1/5th the width of the chemical energy arrow. The heat & sound arrow should be 4/5th the width of the chemical energy arrow.

  35. Improving efficiency Decrease loss to heat by: Reducing friction by using a lubricant (eg oil). Reducing electrical resistance in electrical circuits. Reducing air resistance by using streamlined shapes. Reduce loss to sound by tightening the loose parts of machinery.

  36. Choose appropriate words to fill in the gaps below: Energy is required to do ________. Energy is measured in ________ (J) Energy cannot be created or ___________ but can only change ________. Kinetic energy is the energy possessed by __________ bodies. When an object is lifted up it gains gravitational _____________ energy. Heat or __________ energy is often produced as a _________ energy form. work joules destroyed form moving potential thermal wasted WORD SELECTION: potential moving joules thermal destroyed wasted form work

  37. Energy and efficiencyNotes questions from pages 44/248 & 45/249 • Explain how energy in joules is related to weight and height. • What is a ‘Sankey diagram’? Draw an example. • Copy the equation defining efficiency on page 44/248. • Calculate the efficiency of a light bulb if it supplies 16J of light when supplied with 80J of electrical energy. • Copy out the table headed ‘Improving efficiency’ on page 45/249. • Copy and answer questions (a), (b), (c) and (d) on pages 44 and 45/249. • Copy the Key Points on page 45/249. • Answer the summary questions on page 45/249.

  38. In text questions: You use your muscles, so the gravitational potential energy is transformed in them to thermal energy. 85 J It is transformed to heat energy in the lamp holder and the surroundings 4 Summary questions: (a) Supplied to. (b) Wasted by. (c) Supplied to, wasted by. (a) 36 J (b) 0.40 (or 40%) 3. 800 J Energy and efficiency ANSWERS

  39. Energy and efficiency issuesNotes questions from pages 46/250 & 47/251 • Answer questions 1 and 2 on page 47/251.

  40. Energy and efficiency issuesANSWERS 1. (a) It uses less fuel per kilometre. (b) Electric cars can’t go very far without being recharged. 2. (a) The hybrid car. (b) £10.20

  41. Energy Conservation - 'Whys Guy' Video Clip (4:40 mins) - Includes Bowling Ball Pendulum Demonstration Sequential Puzzle on Energy Size - by KT  - Microsoft WORD Hidden Pairs Game on Energy Transfers - by KT - Microsoft WORD Energy conversions & efficiency calculations - eChalk Energy transfer bounce quizes - eChalk BBC AQA GCSE Bitesize Revision: Introduction Page on AQA Heat Transfer & Efficiency Forms of energy table Energy transfer examples including Sankey Diagram Efficiency with Sankey Diagrams and a calculation example Test bite on Heat transfer, Energy transfers & Efficiency BBC KS3 Bitesize Revision: KS3 Energy Resources and Energy Transfer Contents Page Energy basics Energy transfer diagrams - includes Sankey type Saving energy - includes power station applet Test bite on KS3 Energy resources and transfer Simulations

  42. How Science WorksANSWERS • Correctly labelled graph with height on the Y-axis and temperature on the X-axis. The line of best fit should be a CURVE. • 1 mm • Rapid initial increase in bounce height. Rate of increase decreases at higher temperatures. • Prediction correct in the range 3oC to 51oC. But overall it is not fully supported. • Yes. Points are not exactly on the line of best fit. Also final result is lower than previous one. • Yes. All but one of the results appear to be 3cm below those of the manufacturer. • The bounce height of the ball will increase whilst the ball is warming up.

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